In general, an irreversible mechanism that prevents transmission, to an input shaft side, of back drive torque to be transmitted from an output shaft side is known. Such an irreversible mechanism is disclosed in Japanese Patent Laying-Open No. 2007-332986, for example.
An irreversible mechanism disclosed in the aforementioned Japanese Patent Laying-Open No. 2007-332986 includes an input shaft, an output shaft, a multi-plate brake, and a screw feed mechanism that connects the output shaft to the multi-plate brake. The multi-plate brake includes multiple first friction plates mounted on a housing and multiple second friction plates mounted on the screw feed mechanism. The first friction plates and the second friction plates each are provided along a radial direction and are alternately aligned in an axial direction. When back drive torque acts on the output shaft, the screw feed mechanism translates rotation of the output shaft to axial displacement, and the second friction plates are pressed against the first friction plates. Thus, when back drive torque acts on the output shaft, the output shaft is fixed, and transmission of back drive torque to an input shaft side is prevented.
This irreversible mechanism is applied to a power transmission system of an aircraft, a general industrial machine, or the like. For example, in the aircraft, the irreversible mechanism is applied to a rudder face (flap) driving device for steering, and transmission of back drive torque from a rudder face side (output shaft side) to an input shaft side can be prevented.